Process for effecting ester condensations



Patented May 12, 1931 UNITED STATES mire CE'AUL HALBIG AND FELIX KAUFLER. on MUNICH, eE-nMnnY, assienons TOW 1m.

ALEXANDER WAGKER GESELLSCI-IAJET FUR ELEKTROCHEMISCHE INDUSTRIE,

MUNICH, GERMANY, A CORPORATION rnocnss roa EFFEGTLCNG Esme connnizsA'rroiis No Drawing. Application filed April 19, 1929, Serial 1T0. 356,595, and in dermany May 14,1923.

The invention relates to processes of effecting condensations of esters or of esters and ketones, such condensations being typified by the well known acetoacetic ester synthesis in which two molecules of ethyl acetate are condensed. The invention relates more particularly to effecting the condensation by means of alkali metal alcoholates.

An object of this invention is to provide a process whereby the alcoholate exerts a strong condensing influence on the esters without the use of extremely high temperatures of greater than atmospheric pressure.

Condensations of esters can be carried out by the use of an alkali metal instead of an alkali metal alcoholate and commercially the alkali metal is used for this purpose because it gives a higher yield of ester condensation under practical working conditions. However, the use of an alkali metal is not eflicient because it induces side reactions which are wasteful. So, for example, the yield of acetoacetic ester from a process using metallic sodium is far greater than the yield from a process using sodium alcoholate, even at higher temperature and pressure, despite the wasteful side reactions in the former process. It can thus be seen that in processes heretofore used, the alcoholate has a weak influence on the esters while alkali metal, though wasteful, has a far greater influence on the esters.

We have made the unexpected discovery that remarkably high yields of ester condensations can be obtained with metal alcoholates if the alcohol formed by the reaction is distilled off during'the reaction. By this expedient the process can be carried out at commercially feasible temperatures and at atmospheric or slightly above atmospheric pressure.

Our process is applicable to any of the condensations known, such as the condensation of two molecules of ethyl acetate, a molecule of ethyl formate and a molecule of ethyl acetate, a molecule of ethyl acetate and a molecule of acetone, etc. All of these condensations required high temperatures and pressures heretofore if an alcoholate was used and the yields obtained were poor,

The following specific examplesyin which the partsare by weight, illustrate the invention.

Ewample 1.'Sixty-eight parts of sodium alcoholate and 650 parts of ethyl acetate were placed in a vessel equipped with a condensing column and heated to the boiling point of the mixture. The column was adjusted in length so that all the alcohol formed passed off through the column. The heating was continued until the formation of alcohol ceased;

this can be determined by testing the exit of the condensing column for alcohol vapors. The reaction mass was then acidified to convert the sodium salt formed to acetoacetic ester and the acetoacetic ester layer which separated out was distilled off. A yield of 122 parts of acetoacetic ester was obtained. This is equivalent to 94% of the theoretical y ld- Emma 2.-Ninety'-six parts of sodium butylate are heated with 550 parts of butyl acetate and the resulting butyl alcohol in mixture with butyl acetate is distilled off by means of a column; fresh butyl acetate is added as required. The residue is acidified e. g. with acetic acid. The salt is removed and the ester mixture is fractionated preferably in vacuum. The yield of acetoacetic acid butyl ester passing over at 16 mm. between 100 and 103 amounts to 90% or more, calculated on the basis of the sodiumbutylate employed.

Example 3.110 parts of sodiumamylate are heated with 650 parts amylacetate and are treated as in Example 1. The yield of acetoacetic acid amyl ester boiling point 105-108 at 16 mm. amounts to over 80% on the basis of the sodiumamylate employed.

The invention claimed is:

1. Process for effecting the condensation of esters comprising heating an alkyl ester of aliphatic monocarboxylic acid in the presence of an alkali metal alcoholate and distilling off the alcohol formed thereby during the reaction.

2. Process for effecting the condensation of esters comprising heating an alkyl ester of aliphatic monocarboxylic acid in the presence of an alkali metal alcoholate and distilling ofi substantially all the alcohol formed thereby during the reaction.

3. Process for effecting the condensation of esters comprising heating an alkyl ester of aliphatic monocarboxylic acid in the presence of an alkali metal alcoholate, distilling oil the alcohol formed thereby during the reaction, adding acid to the reaction mixture after formation of alcohol ceases to liberate the ester condensation and distilling said mixture to recover said ester condensation.

4. Process for effecting the condensation of esters comprising heating ethyl acetate in the presence of an alkali metal alcoholate and distilling 011? the alcohol formed thereby during the reaction.

5. Process for eflecting condensation of esters comprising heating ethyl acetate in the presence of an alkali metal alcoholate, distilling off the alcohol formed thereby during the reaction, adding acid to the reaction mixture after formation of alcohol ceases, to liberate the acetoacetic ester and distilling said mixture to recover the acetoacetic ester.

6. Process for effecting condensation of esters comprising heating ethyl acetate in the presence of sodium alcoholate, distilling ofi the alcohol formed thereby during the reaction, adding acid to the reaction mixture after formation of alcohol ceases, to libcrate the acetoacetic ester and distilling said mixture to recover the acetoacetic ester.

Signed at Munich, State of Bavaria, this eighth day of April, A. D. 1929.

DR. PAUL HALBIG. DR. FELIX KAUFLER. 

